桥式超导故障限流器的研究新进展

普通桥式超导故障限流器(Superconducting Fault Current Limiter,SFCL)只能限制故障短路电流的峰值,不能限制短路电流的稳态值。应用电力电子技术对桥式超导限流器的结构进行改进能在保持原有桥式限流器优点的基础上,有效限制短路电流的稳态值。针对现今的研究热点,着重介绍了全控桥型、电阻投切型、混合型、有源型等几种实用价值较高的桥式SFCL的工作原理及其特点,并对桥式超导限流器研究中存在的问题及其发展趋势做了说明。     

电压补偿型超导限流器在三相电网中的故障限流特性

基于电压补偿型超导故障限流器(SFCL)的单相电路结构和工作原理,提出了一种关于电压补偿型超导故障限流器的三相电路结构,并对其在三相电力系统发生不同故障时的运行特性进行了分析。利用Matlab/simulink建立仿真模型,仿真结果表明该电压补偿型SFCL的三相拓扑结构具有一定的可行性,对系统中发生不同短路故障时的短路电流都具有良好的限制作用。     

超导故障限流器螺旋线圈交流损耗特性的研究

超导故障限流器(SFCL)是超导电力应用的一个重要器件,本文采用Bi-2212和YBCO材质的高温超导体来制作SFCL,其具有大容量电流和高电场的优点。作为22. 9kV/25MVA配电系统中SFCL的初期应用阶段,为减少SFCL的交流损耗,制备几种形状线圈的故障电路限制元器件,通过实验研究导体排列和电力方向对故障限流线圈交流损耗特性的影响。经测试,单线型和双线型螺旋线圈的交流损耗均依赖于导体的排列和电流方向,双线型螺旋线圈在导体排列相同的情况下,其交流损耗取决于电流方向。     

电压补偿型超导限流器对电流保护的影响

基于电压补偿型超导故障限流器(SFCL)的工作原理,分析了电网故障时由于限流器限流阻抗串入对电流保护的影响.通过重新整定电流保护的动作值,得到了限流器与电流保护配合的解决方法.以一个10kV中性点不接地配电网为例,分别对引入SFCL前后系统三相短路的电流保护进行仿真,验证了该方法的有效性.     

高温超导故障限流器稳态与瞬态三维仿真与分析

采用三维有限元场-路耦合方法和磁路方法研究饱和铁芯型超导限流器(SFCL)的瞬态过程,并针对故障状态时,直流超导线圈感应高电压现象,提出使用短路线圈改善超导线圈的高压问题。通过与限流器样机的试验结果对比分析,证明数值计算方法的正确性。     

电力故障运行下磁偏置超导限流器超导限流单元的电-热特性分析与验证

本文的磁偏置高温超导故障限流器(SFCL)是一种新型超导限流器,在系统出现短路故障时,发生失超现象,产生高阻抗限制短路电流,达到一定时间后断开超导单元,再由双分裂电抗器二次限流.当短路电流消失后,自动快速恢复到无阻特性,然后重新合闸投入系统运行.在SFCL并网运行前,要对并网运行中出现相间短路等故障的暂态运行特性进行分析,了解并网运行时的状况.本文利用Matlab/Simulink构建了SFCL的仿真分析模型,包含超导限流单元的等效电路模型和热模型.该模型被接入一个由Matlab/Simulink构建的10 kV电力系统模型中,用来仿真SFCL的并网运行特性.仿真结果表明了SFCL在并网运行中的效果,以及相间短路故障下失超电阻、通过电流和超导限流单元温度的变化.同时,在中国国网辽宁电力虎石台对SFCL进行了并网运行试验,得到了相间短路故障下的暂态运行特性和失超恢复时间.本文的仿真分析和试验结果,证明了该SFCL样机具备10 kV并网能力,以及快速响应、逐级限流和快速恢复能力     

新型磁屏蔽感应型超导故障限流器的研究

在研究磁屏蔽感应型超导故障限流器原理的基础上,提出了一种新型磁屏蔽感应型高温超导故障限流器,它主要由一次超导绕组、二次超导圆柱形屏蔽筒、铁芯和液氮冷冻箱组成,其工作原理是利用超导绕组和超导筒从超导态转变到正常态时其阻抗的快速上升而限流,对应用于三相系统的新型磁屏蔽感应型超导故障限流器进行了仿真研究,它能显著地减少暂态及稳态的故障电流,有效地提高电力系统的稳定性.     

电阻型超导限流器故障限流引发的传热问题研究

为研究用于电阻型超导限流器(SFCL)故障限流引发的传热问题,本文采用12mm宽、0.31mm厚的纯不锈钢带材模拟电阻型限流器专用第二代(2G)高温超导带材,通过电加热方式获得其在液氮中不同放置状态的沸腾热流密度曲线,并修正经典模型系数以适用于描述故障限流后巨大温差等复杂换热工况下的传热规律;同时通过淬冷法获得不锈钢及2G超导带材的淬冷沸腾热流密度曲线。     

饱和铁芯型超导限流器研究进展综述

电力系统短路电流对系统的稳定安全运行造成了极大的威胁,超导故障限流器是一种将超导技术、电力技术相结合产生的故障限流装置,能有效地限制短路电流。饱和铁芯型超导限流器是产业化前景较好的一种超导限流器,在对此类型的故障限流器进行了深入调研和广泛收集资料的基础上,介绍了饱和铁芯型超导限流器的工作原理,分析了它的优缺点,阐述了饱和铁芯型超导限流器的国内外发展现状,归纳了其在设计过程中的关键技术和制约其工业化应用的主要问题,并提出了技术建议,最后展望了饱和铁芯型超导限流的应用前景。     

直流超导限流器的发展和应用现状综述

超特高压直流电网发展迅速,但是直流电网面临故障电流上升速度快、幅值高、切断困难的问题,限流器能够抑制故障电流的上升,降低直流故障电流的开断难度.直流超导限流器是其中极为关键的一类,总结了相关的研究进展,着重介绍了电阻型、磁通耦合型、饱和铁心型、磁屏蔽型超导限流器的工作原理,并且介绍了最新的应用研究.最后讨论了直流超导限...     

超导故障限流器的数学模型研究

文中总结了几种超导故障限流器的模型。在数学模型的基础上 ,阐述了超导材料的温升、失超传播速度和临界电流密度对超导故障限流器性能的影响     

The role of type III factors in quantum field theory

One of von Neumann's motivations for developing the theory of operator algebras and his and Murray's 1936 classification of factors was the question of possible decompositions of quantum systems into independent parts. For quantum systems with a finite number of degrees of freedom the simplest possibility, i.e. factors of type I in the terminology of Murray and von Neumann, are perfectly adequate. In relativistic quantum field theory (RQFT), on the other hand, factors of type III occur naturally. The same holds true in quantum statistical mechanics of infinite systems. In this brief review some physical consequences of the type III property of the von Neumann algebras corresponding to localized observables in RQFT and their difference from the type I case will be discussed. The cumulative effort of many people over more than 30 years has established a remarkable uniqueness result: The local algebras in RQFT are generically isomorphic to the unique, hyperfinite type III, factor in Connes' classification of 1973. Specific theories are characterized by the net structure of the collection of these isomorphic algebras for different space-time regions, i.e. the way they are embedded into each other     

Control strategy for three-phase four-wire PWM converter of integrated voltage compensation type active SFCL

The integrated voltage compensation type active superconducting fault current limiter (SFCL) is composed of three air-core superconducting transformers and a three-phase four-wire PWM converter. In order to realize the current-limiting characteristics of the integrated active SFCL, it is needed to control the three-phase four-wire PWM converter flexibly and reasonably. Thereby, the control strategy for the converter is analyzed in this paper. In dq0 reference frame, the mathematical model of the converter is founded. The double-loop control strategy, consisting of voltage outer loop and current inner loop, is presented. Moreover, the voltage balance control for the split DC link capacitors is also considered. Using MATLAB, the simulation model of the integrated active SFCL is built. According to the simulation results, it is known that, the presented control strategy is feasible and valid, and the converter can work well under unsymmetrical and symmetrical fault conditions, and then the fault current can be limited quickly and effectively.     

Superconducting fault current limiter for railway transport

A resistive switching superconducting fault current limiter (SFCL) for DC networks with voltage of 3.5 kV and nominal current of 2 kA is developed. The SFCL consists of two series-connected units: block of superconducting modules and high-speed vacuum breaker with total disconnection time not more than 8 ms. The results of laboratory tests of superconducting SFCL modules in current limiting mode are presented. The recovery time of superconductivity is experimentally determined. The possibility of application of SFCL on traction substations of Russian Railways is considered.     

A superconducting direct-current limiter with a power of up to 8 MVA

A resistive switching superconducting fault current limiter (SFCL) for DC networks with a nominal voltage of 3.5 kV and a nominal current of 2 kA was developed, produced, and tested. The SFCL has two main units—an assembly of superconducting modules and a high-speed vacuum circuit breaker. The assembly of superconducting modules consists of nine (3 × 3) parallel–series connected modules. Each module contains four parallel-connected 2G high-temperature superconducting (HTS) tapes. The results of SFCL tests in the short-circuit emulation mode with a maximum current rise rate of 1300 A/ms are presented. The SFCL is capable of limiting the current at a level of 7 kA and break it 8 ms after the current-limiting mode begins. The average temperature of HTS tapes during the current-limiting mode increases to 210 K. After the current is interrupted, the superconductivity recovery time does not exceed 1 s.